Apparatus for fabricating a reinforced plastic article



March 3, 1964 J, REED 3,123,313

APPARATUS FOR FABRICATING A REINFORCED PLASTIC ARTICLE Original FiledMay 8, 1959 INVENTOR. DANIEL J. REED Andrus 5; Starlge Attorneys UnitedStates Patent 3,123,313 APPARATUS FOR FABRICATING A REINFGRCED PLASTICARTlCLE Daniel J. Reed, Milwaukee, Wis., assignor to A. 0. SmithCorporation, Milwaukee, Wis., a corporation of New York Originalapplication May 8, 1959, Ser. No. 811,834, new Patent No. 2,987,217,dated June 6, 1961. Divided and this application Oct. 25, 1960, er. No.64,905

4 Qlaims. (Cl. 242-7) This invention relates to the manufacturing ofirregularly shaped articles and more particularly to the forming of areinforced plastic vessel with an integral, irregularly shaped head.

Reinforced plastic vessels have recently found increased use because oftheir light weight and corrosion resistance to most corrosive media.Generally, a reinforced plastic vessel is formed of a cylindrical shellwhich may be fabricated by Winding substantially continuous reinforcingfibers around the mandrel, or alternately, by laying up glass matting orfabric into a cylindrical or tubular form. In the conventional vessel, amolded head is then secured into the open ends of the cylindrical shellto form the vessel.

It has been proposed to form a reinforced plastic vessel by winding thehead integrally with the shell. In a method such as this, the mandrel isprovided with a circumferential slot and the fibrous strand is wound inthe slot until the winding is flush with the periphery of the mandrel toform the head of the vessel. Additional windings of the fibrous strandare made over the peripheral surface of the vessel to form the wall ofthe vessel.

A winding method such as this may be satisfactorily used whenfabricating a generally cylindrical vessel, but is not suitable whenfabricating vessels of rectangular or irregular shape. For example, witha rectangular vessel, the distance from the axis to the midpoint of theside walls is less than the distance from the axis to the corners sothat the windings made within the slot to form the head will not besubstantially flush over the entire periphery of the slot.

The present invention is directed to a method of fabricating anirregularly shaped vessel with an integral head, and to a mandrelconstruction for fabricating the vessel.

More specifically, an irregularly shaped mandrel having a contourcorresponding to the desired contour in the vessel, is provided with acircumferential slot which extends radially inward to a locationadjacent the axis of the mandrel. The slot is formed such that the areaof all radial planes in the slot are substantially equal. With anon-circular mandrel, this requires that the width of the slot vary inaccordance with the change in the length of the radii of the mandrel.

A reinforcing strip impregnated with a suitable resin or binder isinitially wound in the slot and due to the cross sectional area beingequal on all radii, the windings will completely fill all port-ions ofthe slot. After the windings are flush with the periphery of themandrel, the Winding is continued over the peripheral surface of themandrel to produce the vessel wall. After the desired number of layersof the fiber strip have been wound over the peripheral surface of themandrel to provide the vessel wall with the desired strength, the res-inis cured to provide a hard integral structure. After curing, the vesselis removed from the mandrel and the central hole in the head is closedoff with a suitable plug.

The present invention provides a simple and inexpensive method ofproducing an irregularly shaped vessel with an integral head. The methodproduces the vessel in a single winding operation and thereby eliminatesthe separate forming operation which is usually required for the "icehead and also the operation of assembling a separate head with the shellas is required in the conventional method of fabricating a reinforcedplastic vessel.

Other objects and advantages will appear in the course of the followingdescription. The drawings illustrate the best mode presentlycontemplated of carrying out the invention.

In the drawings:

FIGURE 1 is a side elevation of the mandrel to be used in fabricatingthe vessel according to the method of the invention;

FIG. 2 is a view taken along line 2?. of FIG. 1;

FIG. 3 is a diagrammatic representation showing the area of two radialplanes within the slot;

FIG. 4 is a perspective view with parts broken away in section sowing avessel fabricated according to the method of the invention;

FIG. 5 is a transverse section of the vessel of FIGA;

FIG. 6 is a vertical section taken along line 6-6 of FIG. 5; and

FIG. 7 is a view similar to FIG. 4 showing a modified form of the vesselin which the vessel is provided with a generally rectangular crosssection.

The drawings illustrate a mandrel 1 having a generally oval crosssectional shape which is secured to a central shaft 2. A disc 3 is alsosecured to the shaft 2 in spaced relation \with an end of the mandrel 1to provide a slot 4 therebetween with the dimension of any radius ofsaid slot being different than the dimension of any othercircumferentially displaced radius through at least a portion of thecircumferential extent of said slot.

The end surface 5 of the disc 3 which faces the mandrel 1 issubstantially flat in contour, while the opposed end wall 6 of themandrel 1 is contoured to provide raised portions 7 which extendgenerally along the long axis of the oval mandrel and lowered portions 8which conform generally to the short axis of the mandrel.

The end wall 6 of the mandrel is formed so that the area of all radialplanes extending longitudinally within the slot 4 will vbe substantiallyequal. As shown in FIG. 3, the radial plane A, which extendslongitudinally of the mandrel and is taken through the slot on the shortradius of the mandrel, is of substantially constant thickness, While theradial plane B, which also extends longitudinally of the mandrel and istaken along the long axis of the mandrel 1 within the slot, has aprogressively decreasing width. This results in the area of planes A andB being substantially equal even though the length of the radii isdiiferent. Thus, all radial planes extending within the slot 4 from theshaft 2 to the peripheral surface of the mandrel 1 have the same area.

A fibrous reinforcing strand 9 impregnated with a suitable binder iswound within the slot 4 until the windings are substantially flush withthe peripheral surface 10 of mandrel 1 and then the strand 9 is woundover the outer surface of the mandrel to form the wall of the vessel.

The reinforcing strand is preferably formed of long, substantiallycontinuous fibers and may take the form of mineral fibers, such as glassor asbestos, vegetable fibers, animal fibers, synthetic fibers, such asnylon, rayon, Dacron or the like. The strand 9 has a width substantiallysmaller than the width of slot 4, so that the strand will readily fillin all portions of the slot, particularly adjacent the contoured endwall 6.

The binding material, which is supplied to the reinforcing strand 9, maytake the form of a thermosetting resin, such as an epoxide resin,polyester, urea, formaldehyde and the like. The resin is applied to thefibrous material by any conventional method, such as spraying, dipping,sloshing and the like.

The portion of the reinforcing strand 9, which is wound within the slot4, forms the head 11 of the vessel and the portion of the strand whichis wound over the peripheral surface of the mandrel 1, forms the shell12, as shown in FIG. 4. By constructing the slot 4 such that the area ofall radial planes extending within the slot is substantially equal, theentire slot Will be filled with the strand without any gaps betweenturns or convolutions. In addition, the strand wound within the slotwill be under uniform tension throughout the entire extent of the slotwithout any portion of the wound strand being in a slack condition.

After the winding has been completed and the desired number of layers ofthe reinforcing strand have been wound over the peripheral surface ofthe mandrel It to provide the vessel wall with the desired strength, theentire assembly is heated to a temperature sufficient to cure the resin.After the curing, the disc 3 is removed from the shaft 2 and the vesselis stripped from the mandrel 1. The central hole 13 in the head 11 ofthe vessel, which is formed by the shaft 2, is enclosed by a suitableplug.

As shown in HS. 4, the bottom surface 14 of the head 11, which wasformed in contact with the flat Wall 5 of disc 3, is substantially flat,while the upper surface 15 of the head 11 has a generally undulatingcontour corresponding to the end wall 6 of mandrel 1. it is to be notedthat all radial planes, indicated by C, D, E and F, have substantiallythe same cross sectional area.

FIG. 7 shows a modified form of the vessel in which the cross section ofthe vessel is generally rectangular. In this case, the upper surface 16of the head 11 is generally flat and is formed by using a generally flatend wall 6 on the mandrel. In this case, the bottom surface 17 of thehead has an undulating contour produced by forming the end wall 5 ofdisc 3 with the desired contour. As in the case of the vessel shown inFIG. 4, the radial planes G, H, I and I all have the identical area. inFIG. 7, however, the planes G, H, l and I all have a substantiallyuniform width throughout their radial extent, while in FIG. 4, the widthof the planes varied throughout their length. In each vessel, however,the area of the radial planes is substantially uniform.

While the description has shown heads of oval and generally rectangularshape being formed by the method of the invention, it is contemplatedthat the vessel and head may have any desired contour except a concavityin the periphery. As the reinforcing material is wound under tension, areinforcing material would merely bridge or arch over the conca ity.

While the above description is directed to a method of making a vesselhaving an integral head, it is contemplated that the mandrel oi theinvention can be employed for making any type of an irregularly shapedplate or disc in the same manner as it is used to make the head of avessel. Similarly, while the disclosure shows the slot 4 being in aplane substantially normal to the axis of mandrel 1, it is contemplatedthat the slot can be formed angularly or it can have a substantiallycurved extent.

This application is a divisional application of copending applicationSerial No. 811,834, filed May 8, 1959, and entitled Reinforced PlasticArticle and Structure for Forming the Same, now Patent No. 2,987,217.

Various modes of carrying out the invention are contemplated as beingWithin the scope of the following claims particularly point ng out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. In an apparatus for fabricating a reinforced plastic vessel articlefrom a substantially continuous strand, a mandrel having a generallynon-circular cross section and having a circumferential slot thereinwith the dimension of any radius of said slot being different than thedimension of any other circumferentially displaced radius through atleast a portion of the circumferential extent of said slot, and the areaof all longitudinally extending radial planes extending within the slotbeing substantially equal when measured from the bottom of the slot tothe periphery of the mandrel and between the opposed walls of the slot.

2. In an apparatus for fabricating a reinforced plastic vessel having anintegral head, a mandrel having a pcripheral surface disposed to supporta strand wound thereon in a generally helical pattern and at least aportion of the radii in any transverse plane in said mandrel being of adifferent length, said mandrel having a cir .imferential slot thereinwith the dimension of any radius of said slot being different than thedimension of any other circumferentially displaced radius through atleast a portion of the circumferential extent of said slot, and means onat least one transverse surface bordering the slot for maintaining thearea of all longitudinally extending radial planes within the slotsubstantially equal when measured from the bottom of the slot to theperiphery of the mandrel and between the opposed walls of the slot.

3. In an apparatus for fabricating a reinforced plastic vessel having anintegral head, a mandrel having a peripheral surface disposed to supporta strand wound thereon in a generally circumferential pattern and withthe length of any radius'of said slot being different than the length ofat least a portion of other circumferentially displaced radii of saidslot, a shaft connected axially to said mandrel, a forming memberconnected to said shaft and having an end surface spaced axially from anend surface of said mandrel to provide a slot therebetween, andcontoured means associated with at least one of said end surfaces formaking the area of all longitudinally extending radial planes within theslot substantially equal when measured from the bottom of the slot tothe periphery of the mandrel and between the opposed walls of the slot.

4. In an apparatus for fabricating a reinforced plastic vessel having anintegral head, a mandrel having a peripheral surface disposed to supporta strand wound thereon in a generally helical pattern, a shaft connectedaxially to said mandrel, a forming member connected to said shaft andhaving an end surface spaced axially from an end surface of said mandrelto provide a slot therebetween with the dimension of any radius of saidslot being different than the dimension of any other circumferentiallydisplaced radius through at least a portion of the circumferentialextent of said slot, and contoured means associated with at least one ofsaid end surfaces for making the area of all longitudinally extendingradial planes within the slot substantially equal when measured from thebottom of the slot to the periphery of the mandrel and between theopposed walls of the slot.

References Cited in the file of this patent UNITED STATES PATENTS2,277,602 Novak Mar. 24, 1942 2,446,490 Scherer Aug. 3, 1948 2,641,299Bloom et al. g June 9, 1953

1. IN AN APPARATUS FOR FABRICATING A REINFORCED PLASTIC VESSEL ARTICLEFROM A SUBSTANTIALLY CONTINUOUS STRAND, A MANDREL HAVING A GENERALLYNON-CIRCULAR CROSS SECTION AND HAVING A CIRCUMFERENTIAL SLOT THEREINWITH THE DIMENSION OF ANY RADIUS OF SAID SLOT BEING DIFFERENT THAN THEDIMENSION OF ANY OTHER CIRCUMFERENTIALLY DISPLACED RADIUS THROUGH ATLEAST A PORTION OF THE CIRCUMFERENTIAL EXTENT OF SAID SLOT, AND THE AREAOF ALL LONGITUDINALLY EXTENDING RADIAL PLANES EXTENDING WITHIN THE SLOTBEING SUBSTANTIALLY EQUAL WHEN MEASURED FROM THE BOTTOM OF THE SLOT TOTHE PERIPHERY OF THE MANDREL AND BETWEEN THE OPPOSED WALLS OF THE SLOT.